The monster GX10ES was a very short-lived model and a US-only export model, as no european or japanese catalog I own does mention it.
Three tone controls with selectable turnovers (like in the old days :), copper-plated chassis, a healthy STD-structured power supply and transformer, five S-video connectors and an IR remote the size of a little book - the works !
Acceptable sources include D.A.T. and CD-V (aka Laserdisc).
This is Sony's last audio receiver that remained strictly 2-channel, too, and that didn't convert every analogue signal into digital for surround-sound effects, like the TA-E1000ESD or TA-E9000ES would do.
As usual, Sony kept very discrete about this "last stand for quality" receiver.
The production run is supposed to have been set at 2000 units but one recently resurfaced with a #802 005 serial number 2005) and another with a #202 265 (2011) - very rare nevertheless.
The same happened to the earlier STR-7800SD which, as all high-end receivers, was export-only.
A step above in this lineup was the very successful TA-E77ESD & TA-N77ES bestselling combo.
A step below were the STR-GX9ES, STR-GX7ES and STR-GX5ES, the latter having been briefly available in Europe.
The STR-GX10ES was in 1990/91 replaced by the STR-GX90ES which, although slightly down-sized plugs-wise and componentry-wise, was no toy either.